Not Applicable.
1. Field of the Invention
The present invention relates to the field of hole enlarging methods and apparatus and in particular to a pilot hole drilling and guiding arrangement for drilling enlarged holes using an existing hole as a pilot guide.
2. Description of Related Art
As can be seen by reference to the following U.S. Pat. Nos. 5,871,310; 2,874,616; 5,143,489; 5,366,326, the prior art is replete with myriad and diverse hole drilling arrangements.
While all of the aforementioned prior art constructions are more than adequate for the basic purpose and function for which they have been specifically designed, they are uniformly deficient with respect to their failure to provide a simple, efficient, and practical device that employs an existing pilot hole to guide an enlarged cutter head into the workpiece in a continuous operation.
As most craftsmen are all too well aware, an inordinate amount of time is expended in enlarging existing pilot holes in workpieces which must then be subjected to a cutting process with or without the use of a separate guide element to enlarge the radius of an existing pilot hole to arrive at an enlarged finished hole diameter.
As a consequence of the foregoing situation, there has existed a longstanding need among craftsmen for a new and improved cutting drill bit arrangement wherein the pilot hole guide is axially aligned with and projects outwardly from the finished hole bit so that the pilot hole guides the finished hole drill bit in a single continuous sequence; and the provision of such an arrangement is the stated objective of the present invention.
Briefly stated, the hole enlarging drill bit that forms the basis of the present invention comprises in general a shaft unit, a pilot hole guiding unit and a finished hole cutting unit deployed in a concentric staggered fashion on the shaft unit.
As will be explained in greater detail further on in the specification, the pilot hole guiding unit fits inside and projects beyond the lower end of the finished hole cutting unit such that after the shaft unit has been operatively connected to a conventional power drill, the power drill can be actuated to enlarge the radius of the existing pilot hole.